[PATCH v2 0/1] rust: add `rustcheck` make target for check-only builds

[PATCH v2 0/1] rust: add `rustcheck` make target for check-only builds

[Onur Özkan]

Changes in v2:
  - Couple of indentation fixes in rust/Makefile.

Onur Özkan (1):
  rust: add `rustcheck` make target for check-only builds

 Makefile      |  7 +++++
 rust/Makefile | 73 +++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 80 insertions(+)

-- 
2.51.0

[PATCH v2 1/1] rust: add `rustcheck` make target for check-only builds

[Onur Özkan]

Adds a new `rustcheck` make target to run a check-only build
similar to `cargo check`. This allows us to verify that the Rust
sources can build without building/linking final artifacts,
which speeds up the iteration (a lot) during development.

The target also supports the CLIPPY flag (e.g., `make LLVM=1
rustcheck CLIPPY=1) to run Clippy in a faster way.

Also, unlike `make LLVM=1`, it doesn't compile large amounts of C
code (on a fresh checkout) when the goal is only to check that
Rust builds are not broken after some changes.

Suggested-by: Benno Losin <lossin@kernel.org>
Link: https://rust-for-linux.zulipchat.com/#narrow/channel/288089/topic/x/near/539103602
Signed-off-by: Onur Özkan <work@onurozkan.dev>
---
 Makefile      |  7 +++++
 rust/Makefile | 73 +++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 80 insertions(+)

diff --git a/Makefile b/Makefile
index cf37b9407821..7812cdc72938 100644
--- a/Makefile
+++ b/Makefile
@@ -1716,6 +1716,8 @@ help:
 	@echo  '		    is formatted, printing a diff otherwise.'
 	@echo  '  rustdoc	  - Generate Rust documentation'
 	@echo  '		    (requires kernel .config)'
+	@echo  '  rustcheck       - Check that the Rust code builds'
+	@echo  '                    (requires kernel .config)'
 	@echo  '  rusttest        - Runs the Rust tests'
 	@echo  '                    (requires kernel .config; downloads external repos)'
 	@echo  '  rust-analyzer	  - Generate rust-project.json rust-analyzer support file'
@@ -1821,6 +1823,11 @@ PHONY += rustdoc
 rustdoc: prepare
 	$(Q)$(MAKE) $(build)=rust $@
 
+# Checking Rust sources.
+PHONY += rustcheck
+rustcheck: prepare0
+	$(Q)$(MAKE) $(build)=rust $@
+
 # Testing target
 PHONY += rusttest
 rusttest: prepare
diff --git a/rust/Makefile b/rust/Makefile
index bfa915b0e588..b45878870207 100644
--- a/rust/Makefile
+++ b/rust/Makefile
@@ -265,6 +265,79 @@ rusttest-kernel: $(src)/kernel/lib.rs rusttestlib-ffi rusttestlib-kernel \
     rusttestlib-uapi rusttestlib-pin_init FORCE
 	+$(call if_changed,rustc_test)
 
+## Check-only compilation (similar to `cargo check`)
+quiet_cmd_rustc_check_library = $(RUSTC_OR_CLIPPY_QUIET) CHECK $<
+      cmd_rustc_check_library = \
+        OBJTREE=$(abspath $(objtree)) \
+        $(RUSTC_OR_CLIPPY) $(rust_common_flags) \
+                @$(objtree)/include/generated/rustc_cfg $(rustc_target_flags) \
+                --crate-type $(if $(rustc_check_library_proc),proc-macro,rlib) \
+                $(if $(rustc_check_library_proc),,--emit=metadata) \
+                --out-dir $(objtree)/$(obj)/check -L$(objtree)/$(obj)/check \
+                --crate-name $(if $(rustc_check_crate_name),$(rustc_check_crate_name), \
+				$(subst rustcheck-,,$(subst rustchecklib-,,$@))) $<
+
+rustcheck: rustchecklib-build_error rustchecklib-ffi rustchecklib-macros \
+	rustchecklib-compiler_builtins rustchecklib-pin_init_internal \
+	rustchecklib-pin_init rustchecklib-bindings rustchecklib-uapi \
+	rustchecklib-kernel
+
+rustchecklib-build_error: $(src)/build_error.rs FORCE
+	+$(call if_changed,rustc_check_library)
+
+rustchecklib-ffi: $(src)/ffi.rs FORCE
+	+$(call if_changed,rustc_check_library)
+
+rustchecklib-macros: private rustc_target_flags = --extern proc_macro
+rustchecklib-macros: private rustc_check_library_proc = yes
+rustchecklib-macros: $(src)/macros/lib.rs FORCE
+	+$(call if_changed,rustc_check_library)
+
+rustchecklib-compiler_builtins: private rustc_check_crate_name = compiler_builtins_kernel
+rustchecklib-compiler_builtins: $(src)/compiler_builtins.rs FORCE
+	+$(call if_changed,rustc_check_library)
+
+rustchecklib-pin_init_internal: private rustc_target_flags = --cfg kernel \
+	--extern proc_macro
+rustchecklib-pin_init_internal: private rustc_check_library_proc = yes
+rustchecklib-pin_init_internal: $(src)/pin-init/internal/src/lib.rs FORCE
+	+$(call if_changed,rustc_check_library)
+
+rustchecklib-pin_init: private rustc_target_flags = --extern pin_init_internal \
+	--extern macros --cfg kernel
+rustchecklib-pin_init: $(src)/pin-init/src/lib.rs rustchecklib-macros \
+	rustchecklib-pin_init_internal FORCE
+	+$(call if_changed,rustc_check_library)
+
+rustchecklib-bindings: private rustc_target_flags = --extern ffi
+rustchecklib-bindings: $(src)/bindings/lib.rs \
+	$(obj)/bindings/bindings_generated.rs \
+	$(obj)/bindings/bindings_helpers_generated.rs \
+	rustchecklib-ffi FORCE
+	+$(call if_changed,rustc_check_library)
+
+rustchecklib-uapi: private rustc_target_flags = --extern ffi
+rustchecklib-uapi: $(src)/uapi/lib.rs $(obj)/uapi/uapi_generated.rs \
+	rustchecklib-ffi FORCE
+	+$(call if_changed,rustc_check_library)
+
+ifdef CONFIG_JUMP_LABEL
+rustchecklib-kernel: $(obj)/kernel/generated_arch_static_branch_asm.rs FORCE
+endif
+ifndef CONFIG_UML
+ifdef CONFIG_BUG
+rustchecklib-kernel: $(obj)/kernel/generated_arch_warn_asm.rs \
+	$(obj)/kernel/generated_arch_reachable_asm.rs FORCE
+endif
+endif
+
+rustchecklib-kernel: private rustc_target_flags = --extern ffi --extern pin_init \
+	--extern build_error --extern macros --extern bindings --extern uapi
+rustchecklib-kernel: $(src)/kernel/lib.rs rustchecklib-ffi rustchecklib-pin_init \
+	rustchecklib-build_error rustchecklib-macros rustchecklib-bindings \
+	rustchecklib-uapi FORCE
+	+$(call if_changed,rustc_check_library)
+
 ifdef CONFIG_CC_IS_CLANG
 bindgen_c_flags = $(c_flags)
 else
-- 
2.51.0

Re: [PATCH v2 0/1] rust: add `rustcheck` make target for check-only builds

[Onur]

On Mon, 15 Sep 2025 14:53:10 +0300
Onur Özkan <work@onurozkan.dev> wrote:

> Changes in v2:
>   - Couple of indentation fixes in rust/Makefile.
> 
> Onur Özkan (1):
>   rust: add `rustcheck` make target for check-only builds
> 
>  Makefile      |  7 +++++
>  rust/Makefile | 73
> +++++++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed,
> 80 insertions(+)
> 

Should we document this target on [0]? I think it will be used quite
frequently by Rust developers on the kernel once we land it, so I
think it's worth documenting. I can include a patch for that if others
would agree.

[0]: https://docs.kernel.org/rust/quick-start.html

Regards,
Onur

Re: [PATCH v2 1/1] rust: add `rustcheck` make target for check-only builds

[Nicolas Schier]

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On Mon, Sep 15, 2025 at 02:53:11PM +0300, Onur Özkan wrote:
> Adds a new `rustcheck` make target to run a check-only build
> similar to `cargo check`. This allows us to verify that the Rust
> sources can build without building/linking final artifacts,
> which speeds up the iteration (a lot) during development.
> 
> The target also supports the CLIPPY flag (e.g., `make LLVM=1
> rustcheck CLIPPY=1) to run Clippy in a faster way.
> 
> Also, unlike `make LLVM=1`, it doesn't compile large amounts of C
> code (on a fresh checkout) when the goal is only to check that
> Rust builds are not broken after some changes.
> 
> Suggested-by: Benno Losin <lossin@kernel.org>
> Link: https://rust-for-linux.zulipchat.com/#narrow/channel/288089/topic/x/near/539103602
> Signed-off-by: Onur Özkan <work@onurozkan.dev>
> ---
>  Makefile      |  7 +++++
>  rust/Makefile | 73 +++++++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 80 insertions(+)
> 
> diff --git a/Makefile b/Makefile
> index cf37b9407821..7812cdc72938 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -1716,6 +1716,8 @@ help:
>  	@echo  '		    is formatted, printing a diff otherwise.'
>  	@echo  '  rustdoc	  - Generate Rust documentation'
>  	@echo  '		    (requires kernel .config)'
> +	@echo  '  rustcheck       - Check that the Rust code builds'
> +	@echo  '                    (requires kernel .config)'
>  	@echo  '  rusttest        - Runs the Rust tests'
>  	@echo  '                    (requires kernel .config; downloads external repos)'
>  	@echo  '  rust-analyzer	  - Generate rust-project.json rust-analyzer support file'
> @@ -1821,6 +1823,11 @@ PHONY += rustdoc
>  rustdoc: prepare
>  	$(Q)$(MAKE) $(build)=rust $@
>  
> +# Checking Rust sources.
> +PHONY += rustcheck
> +rustcheck: prepare0

Why do you let rustcheck depend on prepare0 instead of prepare?

> +	$(Q)$(MAKE) $(build)=rust $@
> +
>  # Testing target
>  PHONY += rusttest
>  rusttest: prepare
> diff --git a/rust/Makefile b/rust/Makefile
> index bfa915b0e588..b45878870207 100644
> --- a/rust/Makefile
> +++ b/rust/Makefile
> @@ -265,6 +265,79 @@ rusttest-kernel: $(src)/kernel/lib.rs rusttestlib-ffi rusttestlib-kernel \
>      rusttestlib-uapi rusttestlib-pin_init FORCE
>  	+$(call if_changed,rustc_test)
>  
> +## Check-only compilation (similar to `cargo check`)
> +quiet_cmd_rustc_check_library = $(RUSTC_OR_CLIPPY_QUIET) CHECK $<
> +      cmd_rustc_check_library = \
> +        OBJTREE=$(abspath $(objtree)) \

Have you tried this?

        OBJTREE=$(CURDIR) \

or

        OBJTREE=$(abs_output) \

I'd favor using one of these instead.

Kind regards,
Nicolas

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Re: [PATCH v2 1/1] rust: add `rustcheck` make target for check-only builds

[Onur Özkan]

On Mon, 22 Sep 2025 08:02:36 +0200
Nicolas Schier <nicolas.schier@linux.dev> wrote:

> On Mon, Sep 15, 2025 at 02:53:11PM +0300, Onur Özkan wrote:
> > Adds a new `rustcheck` make target to run a check-only build
> > similar to `cargo check`. This allows us to verify that the Rust
> > sources can build without building/linking final artifacts,
> > which speeds up the iteration (a lot) during development.
> > 
> > The target also supports the CLIPPY flag (e.g., `make LLVM=1
> > rustcheck CLIPPY=1) to run Clippy in a faster way.
> > 
> > Also, unlike `make LLVM=1`, it doesn't compile large amounts of C
> > code (on a fresh checkout) when the goal is only to check that
> > Rust builds are not broken after some changes.
> > 
> > Suggested-by: Benno Losin <lossin@kernel.org>
> > Link:
> > https://rust-for-linux.zulipchat.com/#narrow/channel/288089/topic/x/near/539103602
> > Signed-off-by: Onur Özkan <work@onurozkan.dev> ---
> >  Makefile      |  7 +++++
> >  rust/Makefile | 73
> > +++++++++++++++++++++++++++++++++++++++++++++++++++ 2 files
> > changed, 80 insertions(+)
> > 
> > diff --git a/Makefile b/Makefile
> > index cf37b9407821..7812cdc72938 100644
> > --- a/Makefile
> > +++ b/Makefile
> > @@ -1716,6 +1716,8 @@ help:
> >  	@echo  '		    is formatted, printing a diff
> > otherwise.' @echo  '  rustdoc	  - Generate Rust
> > documentation' @echo  '		    (requires kernel
> > .config)'
> > +	@echo  '  rustcheck       - Check that the Rust code
> > builds'
> > +	@echo  '                    (requires kernel .config)'
> >  	@echo  '  rusttest        - Runs the Rust tests'
> >  	@echo  '                    (requires kernel .config;
> > downloads external repos)' @echo  '  rust-analyzer	  -
> > Generate rust-project.json rust-analyzer support file' @@ -1821,6
> > +1823,11 @@ PHONY += rustdoc rustdoc: prepare
> >  	$(Q)$(MAKE) $(build)=rust $@
> >  
> > +# Checking Rust sources.
> > +PHONY += rustcheck
> > +rustcheck: prepare0
> 
> Why do you let rustcheck depend on prepare0 instead of prepare?
> 

Because "prepare" does more job which isn't necessary (therefore waste
of time) for "rustcheck".

> > +	$(Q)$(MAKE) $(build)=rust $@
> > +
> >  # Testing target
> >  PHONY += rusttest
> >  rusttest: prepare
> > diff --git a/rust/Makefile b/rust/Makefile
> > index bfa915b0e588..b45878870207 100644
> > --- a/rust/Makefile
> > +++ b/rust/Makefile
> > @@ -265,6 +265,79 @@ rusttest-kernel: $(src)/kernel/lib.rs
> > rusttestlib-ffi rusttestlib-kernel \ rusttestlib-uapi
> > rusttestlib-pin_init FORCE +$(call if_changed,rustc_test)
> >  
> > +## Check-only compilation (similar to `cargo check`)
> > +quiet_cmd_rustc_check_library = $(RUSTC_OR_CLIPPY_QUIET) CHECK $<
> > +      cmd_rustc_check_library = \
> > +        OBJTREE=$(abspath $(objtree)) \
> 
> Have you tried this?
> 
>         OBJTREE=$(CURDIR) \
> 
> or
> 
>         OBJTREE=$(abs_output) \
> 
> I'd favor using one of these instead.
> 

I don't have a strong opinion on any of them. I followed the existing
approach from the other use cases used in the same file.

Regards,
Onur

Re: [PATCH v2 0/1] rust: add `rustcheck` make target for check-only builds

[Onur Özkan]

On Mon, 15 Sep 2025 14:53:10 +0300
Onur Özkan <work@onurozkan.dev> wrote:

> Changes in v2:
>   - Couple of indentation fixes in rust/Makefile.
> 
> Onur Özkan (1):
>   rust: add `rustcheck` make target for check-only builds
> 
>  Makefile      |  7 +++++
>  rust/Makefile | 73
> +++++++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed,
> 80 insertions(+)
> 

A friendly ping on this patch. It's been over two weeks with no
feedback, would appreciate any thoughts or suggestions.

Regards,
Onur

Re: [PATCH v2 1/1] rust: add `rustcheck` make target for check-only builds

[Nicolas Schier]

On Tue, Sep 23, 2025 at 06:47:20AM +0300, Onur Özkan wrote:
> On Mon, 22 Sep 2025 08:02:36 +0200
> Nicolas Schier <nicolas.schier@linux.dev> wrote:
> 
> > On Mon, Sep 15, 2025 at 02:53:11PM +0300, Onur Özkan wrote:
> > > Adds a new `rustcheck` make target to run a check-only build
> > > similar to `cargo check`. This allows us to verify that the Rust
> > > sources can build without building/linking final artifacts,
> > > which speeds up the iteration (a lot) during development.
> > > 
> > > The target also supports the CLIPPY flag (e.g., `make LLVM=1
> > > rustcheck CLIPPY=1) to run Clippy in a faster way.
> > > 
> > > Also, unlike `make LLVM=1`, it doesn't compile large amounts of C
> > > code (on a fresh checkout) when the goal is only to check that
> > > Rust builds are not broken after some changes.
> > > 
> > > Suggested-by: Benno Losin <lossin@kernel.org>
> > > Link:
> > > https://rust-for-linux.zulipchat.com/#narrow/channel/288089/topic/x/near/539103602
> > > Signed-off-by: Onur Özkan <work@onurozkan.dev> ---
> > >  Makefile      |  7 +++++
> > >  rust/Makefile | 73
> > > +++++++++++++++++++++++++++++++++++++++++++++++++++ 2 files
> > > changed, 80 insertions(+)
> > > 
> > > diff --git a/Makefile b/Makefile
> > > index cf37b9407821..7812cdc72938 100644
> > > --- a/Makefile
> > > +++ b/Makefile
> > > @@ -1716,6 +1716,8 @@ help:
> > >  	@echo  '		    is formatted, printing a diff
> > > otherwise.' @echo  '  rustdoc	  - Generate Rust
> > > documentation' @echo  '		    (requires kernel
> > > .config)'
> > > +	@echo  '  rustcheck       - Check that the Rust code
> > > builds'
> > > +	@echo  '                    (requires kernel .config)'
> > >  	@echo  '  rusttest        - Runs the Rust tests'
> > >  	@echo  '                    (requires kernel .config;
> > > downloads external repos)' @echo  '  rust-analyzer	  -
> > > Generate rust-project.json rust-analyzer support file' @@ -1821,6
> > > +1823,11 @@ PHONY += rustdoc rustdoc: prepare
> > >  	$(Q)$(MAKE) $(build)=rust $@
> > >  
> > > +# Checking Rust sources.
> > > +PHONY += rustcheck
> > > +rustcheck: prepare0
> > 
> > Why do you let rustcheck depend on prepare0 instead of prepare?
> > 
> 
> Because "prepare" does more job which isn't necessary (therefore waste
> of time) for "rustcheck".
> 
> > > +	$(Q)$(MAKE) $(build)=rust $@
> > > +
> > >  # Testing target
> > >  PHONY += rusttest
> > >  rusttest: prepare
> > > diff --git a/rust/Makefile b/rust/Makefile
> > > index bfa915b0e588..b45878870207 100644
> > > --- a/rust/Makefile
> > > +++ b/rust/Makefile
> > > @@ -265,6 +265,79 @@ rusttest-kernel: $(src)/kernel/lib.rs
> > > rusttestlib-ffi rusttestlib-kernel \ rusttestlib-uapi
> > > rusttestlib-pin_init FORCE +$(call if_changed,rustc_test)
> > >  
> > > +## Check-only compilation (similar to `cargo check`)
> > > +quiet_cmd_rustc_check_library = $(RUSTC_OR_CLIPPY_QUIET) CHECK $<
> > > +      cmd_rustc_check_library = \
> > > +        OBJTREE=$(abspath $(objtree)) \
> > 
> > Have you tried this?
> > 
> >         OBJTREE=$(CURDIR) \
> > 
> > or
> > 
> >         OBJTREE=$(abs_output) \
> > 
> > I'd favor using one of these instead.
> > 
> 
> I don't have a strong opinion on any of them. I followed the existing
> approach from the other use cases used in the same file.

well, you're right, it's not really consistent right now.

Acked-by: Nicolas Schier <nsc@kernel.org>